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# 8066
Last August, in Lancet: Camels Found With Antibodies To MERS-CoV-Like Virus we got our first good look at data suggesting that exposure to MERS-CoV – or a virus closely related to it – was common among camels tested in Oman. The tests were not as definitive as isolating a live virus, of course – as only antibodies to the virus are measured – but it was pretty compelling evidence nonetheless.
Yesterday the journal Eurosurveillance published a pair of studies and an editorial (see Note from the editors: MERS-CoV – the quest for the reservoir continues) that adds substantially to our knowledge about the incidence (or lack, thereof) of MERS-like viruses in camels and major livestock on the Arabian Peninsula, but doesn’t tell us what role they may play in the spread of the disease.
The editors of Eurosurveillance summarize these study’s findings:
The results presented now are compelling evidence that in the studied regions high proportions of dromedary camels are exposed to a MERS-CoV or MERS-like CoV already in their first year of life. Hemida at al. conclude that camels could be infected early in life, and Reusken et al. additionally raise the possibility that the serological reactivity early in life could be due to maternal antibodies.
While the presented studies confirm the potential role of dromedary camels as MERS-CoV reservoir, they do not support a similar role of other common domestic livestock in the affected regions in the Middle East. Neither of the two studies detected antibodies in chicken, cattle or goats. Although most tests in sheep were negative, one particular assay gave positive results in a few animals, and the authors stress that this needs further investigation.
While the papers in today’s issue provide further insight into the possible animal reservoir, the primary source of MERS-CoV infections remains unclear and the link to humans needs to be elucidated further as exposure to animals has only been documented for a limited number of human MERS cases.
The two studies, with a long list of well known authors attached, are:
by CB Reusken, M Ababneh, VS Raj, B Meyer, A Eljarah, S Abutarbush, GJ Godeke, TM Bestebroer, I Zutt, MA Müller, BJ Bosch, PJ Rottier, AD Osterhaus, C Drosten, BL Haagmans, MP Koopmans
Between June and September 2013, sera from 11 dromedary camels, 150 goats, 126 sheep and 91 cows were collected in Jordan, where the first human Middle-East respiratory syndrome (MERS) cluster appeared in 2012. All sera were tested for MERS-coronavirus (MERS-CoV) specific antibodies by protein microarray with confirmation by virus neutralisation. Neutralising antibodies were found in all camel sera while sera from goats and cattle tested negative. Although six sheep sera reacted with MERS-CoV antigen, neutralising antibodies were not detected.
by MG Hemida, RA Perera, P Wang, MA Alhammadi, LY Siu, M Li, LL Poon, L Saif, A Alnaeem, M Peiris
In Saudi Arabia, including regions of Riyadh and Al Ahsa, pseudoparticle neutralisation (ppNT) and microneutralisation (MNT) tests detected no antibodies to Middle East Respiratory Syndrome coronavirus (MERS-CoV) in sheep (n= 100), goats (n= 45), cattle (n= 50) and chickens (n= 240). Dromedary camels however, had a high prevalence of MERS-CoV antibodies. Bovine coronavirus (BCoV) infected sera from cattle had no cross-reactivity in MERS-CoV ppNT or MNT, while many dromedary camels’ sera reacted to both BCoV and MERS-CoV. Some nevertheless displayed specific serologic reaction profiles to MERS-CoV.
Of note is the author’s warning that many dromedary camels had sera displaying reactivity to both MERS-CoV and bovine coronavirus (BCoV) and that `the sera appear to have an unusually broad pattern of cross-reactivity for these related viruses This needs to be considered when interpreting seroepidemiological data by carrying out parallel microneutralisation tests for both MERS CoV and BCoV.’.
Given that bovine coronavirus (BCoV) is fairly common, and is antigenically quite similar to the most commonly reported human coronavirus, (HCoV-OC43), it wouldn’t be unreasonable to expect that some camels could be exposed to both MERS and BCoV (or possibly, even HCoV-OC43) over time.
Last night Robert Roos, Editor of CIDRAP NEWS, produced a terrific summary of both studies which you can read at the link below:
Jordanian, Saudi camels have MERS-CoV-like antibodies
Robert Roos | News Editor | CIDRAP News | Dec 12, 2013
While these studies provide important clues in the spread and host range of MERS-CoV, and they serve to put camels even more into the spotlight, definitive answers as to how the virus is jumping into the human population remain elusive.
